Oilseeds generally contain from about 20% to about 50% oil by weight with the percentages varying with the type of oilseed. Often, oilseed meals are pressed to remove the majority of oil. However, even with pressing, a significant amount of oil remains in the meal. Oil content of the meal can be reduced to about 10-25% by mechanical processing (pressing) and then further processed using various solvents to reduce the oil content to about 3%. The pressed oilseed meal is generally removed using low-boiling organic solvents such as hexane. While these organic solvents can remove additional oil from the oil seed meals by extraction, the use of such organic solvents, even though they may be relatively low boiling, still require elevated temperatures for solvent removal. Elevated temperatures can result in denaturing of the protein, which degrades soluble protein resulting in increased levels of insoluble protein thereby reducing the nutritional value of the product. The use of solvent (other than water) results in environmental issues, as well as recovery and disposal problems in addition to increased energy usage. Even when elevated temperatures are used, residual organic solvent is trapped within the solvent-extracted meal; this residual solvent is difficult to remove without denaturing the protein in the meal.
U.S. Pat. No. 7,156,981 describes the use of an extraction solvent that has an even lower boiling point than hexane. Iodotrifluoromethane (CIF3, also referred to herein as ITFM) alone or with cosolvents, such as HFC-134 can be used at ambient temperature or below with elevated pressures sufficient to keep the solvent in a liquid state, avoiding the need for elevated temperatures and thus significantly reducing the denaturing of the protein. However, because of the need for elevated pressures, the quantity of HTFM required for suitable extraction, high costs of the HTFM and environmental concerns, a more suitable alternative to hexane, HTFM or other extraction techniques is desired.